Supplementary information
In-situ observation and atomic resolution imaging of the
ion irradiation induced amorphisation of graphene
C.-T. Pan1,2, J. A. Hinks3, Q. M. Ramasse4, G. Greaves3 , U. Bangert1,*, S. E. Donnelly3, S. J.
Haigh1
1
School of Materials, University of Manchester, Material Science Centre, Grosvenor Street,
Manchester, M13 9PL, United Kingdom
2
School of Physics and Astronomy, University of Manchester, Manchester, Oxford Road,
M13 9PL, United Kingdom
3
School of Computing and Engineering, University of Huddersfield, HD1 3DH, United
Kingdom
4
SuperSTEM Laboratory, STFC Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD,
United Kingdom
*
Current address: Department of Physics and Energy, University of Limerick, Limerick,
Ireland
Correspondence and requests for materials should be addressed to S. J. Haigh (email:
sarah.haigh@manchester.ac.uk).
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S1. Macroscopic corrugations removed by ion irradiation
a
c
b
1 μm
Supplementary Figure S1 (a) and (b) The evolution of the macroscopic morphology of a
few-layer graphene sheet. (a) Few-layer suspended graphene before irradiation (the red
arrows show the bend contours). The same few-layer graphene sample after 6 keV Ar ion
irradiation at fluences of (b) 6.0×1013 ions cm-2 and (c) 9.0×1013 ions cm-2.
All the results presented in the main text consider 30 keV He ion irradiation. For comparison,
Fig. S1 illustrates the evolution of the macroscopic morphology of a few-layer graphene sheet
during continuous ion irradiation with 6 keV Ar ions. It is expected that 30 keV He ions will
have a similar mechanism of irradiation damage as 6 keV Ar ions as both will produce purely
ballistic interactions with atoms in the lattice. A similar sample thickness to that of the sample
shown in Fig 1 of the main text was estimated in this case (~15 graphene layers found from
the optical image contrast of the flake on a SiO2/Si substrate before it was transferred to the
Quantifoil TEM grid). In the suspended few-layer graphene before irradiation (Fig. S1a), red
arrows point to the bend contours that are observed due to the presence of macroscopic
wrinkles/corrugations. During ion irradiation the bend contours gradually disappeared until
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they were completely removed at a fluence of 6.0×1013 ions cm-2 (Fig. S1b). At a fluence of
9.0×1013 ions cm-2, the few-layer graphene was observed to tear close to the Quantifoil
support film in the lower bottom-right corner (Fig. S1c) probably as a result of the internal
strength of the irradiation damaged graphene becoming less than the force of adhesion
between the graphene sheet and the support film.
S2. Fully amorphous diffraction rings after 30 keV He ion irradiation of
few-layer graphene
Supplementary Figure S2 (a) and (b) TEM images of few-layer graphene with the
corresponding in-situ diffraction patterns shown in (c) and (d). Panels (a) and (c) are before
irradiation with (b) and (d) showing the same sample after irradiation with 30 keV He ions to
a fluence of 2.0×1016 ions cm-2. The scale bars on the images are 2 μm. The few-layer
graphene shown here is suspended on a Ni metal support grid.
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Fig. S2 shows also the removal of bend contours in few-layer graphene (more than 10
layers) after 30 keV He irradiation at a fluence of 2.0×1016 ions cm-2, which gives rise to fully
amorphous diffraction rings (Fig. S2(d)). For comparison inner hexagonal spots are still
weakly observable in the diffraction pattern for single layer graphene irradiated with a
fluence of 1.2×1016 ions cm-2 (Fig. 2g).
S3. Method for peak fitting the Raman spectra
Supplementary Figure S3 Fitting D, G and D’ peaks of the Raman spectra of irradiated
single-layer graphene by 30 keV He to a fluence of (a) 3.0×1015 ions cm-2 and (b) 9.6×1015
ions cm-2.
To calculate I(D)/I(G) it is necessary to perform careful peak fitting for the Raman spectra
at different ion fluences. When the D, G and D’ peaks were all distinguishable, such as at low
irradiation fluences for single-layer graphene, peak fitting was performed using three
Lorentzian functions as shown in Fig. S3(a). For higher fluences the G peak became broader
and merged with the D’ peak. In this case only two Lorentzian functions were used to fit the
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D and G peaks (Fig. S3(b)). When the G peak is very broad, the exact G peak position is
difficult to determine and a better fit has been shown to be achievable using a
Breit-Wigner-Fano (BWF) function for the G peak and the usual Lorentzian fit for the D peak
as described in Ref 1.
(1) Fluence
(30 keV He ions cm-2)
(2)
I(D)/I(G)
(3) LD
(nm)
(4) Estimated Defect
Density (defects cm-2)
3.0×1015
1.06
12
1.0×1012
6.0×1015
1.67
2
3.3×1013
9.6×1015
0.77
1
7.2×1013
Supplementary Table S1: (1) Irradiation fluence, (2) intensity ratio of the D peak to G peak,
(3) LD: average defect distance (as defined in Fig. 3b) estimated from Raman spectra via the
method described in Ref 2 and (4) estimated defect density calculated with   1/ L2D .
S4. Effect of annealing
Supplementary
Figure
S4
Raman spectra of irradiated
graphene after 30 keV He
irradiation with a fluence of
3.0×1015 ions cm-2 before (black
curve) and after (red curve)
annealing at 100°C for 5 hours in
vacuum.
The intensity ratio I(D)/I(G) of an irradiated graphene sheet at a fluence of 3.0×1015 ions
cm–2 decreased from 1.06 to 0.42 after annealing at 100°C in vacuum for 5 hours as shown in
Fig. S4. According to the quantification method in Ref 2, this change corresponds to an
increase in LD from 12 nm to 20 nm. This behaviour is similar to the hysteresis cycle
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described in Ref 1, which suggests some defects were removed after baking. To minimise the
annealing effects on the observation of irradiated graphene, defective graphene samples were
imaged without annealing after irradiation, as shown in Figs. 4-6.
S5. Atomic-resolution HAADF images of irradiated graphene before image
processing
Supplementary Figure S5 (a) to (d) unprocessed raw HAADF images of Fig. 4a-d. The
image filtering process used to obtain the images (Fig. 4a-d) is based on a difference of
Gaussians as reported in Ref 3.
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S6. Atomic resolution HAADF images of irradiated graphene (raw)
Supplementary Figure S6 a(i-iii) Raw HAADF images of Fig. 6a(i-iii) extracted from the
Video S1. b(i-iii) Raw HAADF images extracted from the Video S2 and before image
processing was used to produce Fig. 6b(i-iii).
S7. Supplementary Video S1 and S2
STEM HAADF videos showing atomic imaging of dynamic defect reconstruction effects in
single-layer graphene.
Supplementary References
1
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2
amorphous carbon. Physical Review B 61, 14095-14107 (2000).
Lucchese, M. M. et al. Quantifying ion-induced defects and Raman relaxation length
3
in graphene. Carbon 48, 1592-1597, doi:10.1016/j.carbon.2009.12.057 (2010).
Krivanek O. L. et al. Low Voltage Electron Microscopy: Principles and Applications,
Chapter 6: Gentle STEM of Single Atoms: Low keV Imaging and Analysis at Ultimate
Detection Limits. First edn, (John Wiley & Sons, Ltd, 2013).
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